I like 4.2 grains of WIN WST with a 200 grain HC lead bullet
OR
4.4 grains of WIN 231 with the same bullet. I prefer the RNFP .452 diameter Laser cast or Meister cast.
They work reliably in all my HK USP's including my Elite and my Tanfoglio Witness compact. They have worked in everyone's guns that have tried them and are very accurate.
here's a photo of what that recipe does for me:
These targets were shot at 25 Yards, outdoor range. Bullets were either 200 grain RNFP (LC) or 200 grain SWC (MC) with 4.2 WIN WST and 4.4 WIN 231 respectively. Yes, I wasn't having a good day, I'm usually a little more consistant. I hadn't been shooting in about 2 weeks, so I was out of shape a little
Anyway, these are true 'powder puff' loads, even my 90 lb wife loves to shoot them. Plus the brass falls on the ground right at my feet. Just barely enough 'oomph' to cycle the slide. Origional factory springs in all my guns too. I bet I could download it a little more with lighter springs.
Another nice thing is that the case is barely expanded. In fact, it takes almost no pressure to resize the cases. I've got some brass that I've reloaded more than 30x times, and while the headstamp disappeared long ago, they are still useable.